In Vitro Determination of Cytotoxic Effects of Ten Essential Oils on Prototheca bovis, Which Causes Mastitis in Dairy Cows

Mastitis is a common condition in dairy cattle that causes huge losses globally. The inflammation is caused by the invasion of the teat canal by pathogens, including hard-to-control single-cell microalgae of the genus <i>Prototheca</i>. The aim of the study was the in vitro comparison of the antimicrobial properties of 10 selected essential oils (EOs) and amphotericin B (AMB) against <i>Prototheca bovis</i> strains (PRO3 and PRO7) from different regions in Poland. The antialgal effect was estimated by using toxicity tests. The chemical composition of the EOs was determined by using gas chromatography coupled with mass spectrometry. The tested EOs had significant cytotoxic effects on algal viability. A statistical analysis of the results revealed that the highest biocidal potential, at a concentration of 2%, was demonstrated by lavender, rosemary, and oregano oils, reducing the survival of the <i>Prototheca bovis</i> strains, on average, by 51.21%, 45.83%, and 45.15%, respectively. In comparison, AMB reduced algal viability by an average of 88% compared with the control groups. Further research into the utilization of the biocidal properties of lavender, rosemary, and oregano oil against <i>Prototheca</i> spp. may help to develop new forms of treatments against mastitis caused by this pathogen in the future.